In a number of industrial applications, it is often desirable to treat the surface of an article or substrate in order to protect the substrate from contaminants. This typically includes controlling and enhancing the barrier properties of a surface to, for example, oils, grease, lipophilic materials, water, hydrophilic solutions, and dirt. Examples of such applications include SCOTCH GUARD.RTM. and STAIN MASTER.RTM. surface coating materials for textile articles such as furniture, clothing, and carpets to impart resistance to staining, and also treating articles formed from metal such as precision parts. It is often desirable to apply a surface treatment to an article in order to protect an article from foreign matter while also preserving the desirable physical properties of the article. With respect to textile-related articles for example, it is particularly desirable to maintain aesthetic properties relating to hand, drape, and texture.
For the most part, organic solvents such as hydrocarbons, chlorinated solvents, and chlorofluorocarbons (CFCs) have been employed in treating various substrates. Recently, however, the use of these solvents has been increasingly disfavored due to heightened environmental concerns. As one alternative, aqueous-based systems have been proposed for treating various articles. The use of the aqueous-based systems, however, also suffers from possible drawbacks, For example, contacting an article with water often adversely affects the physical properties of the article. For example, the texture and drape of a textile can be negatively impacted, or flash rusting of metal parts may occur due to water contact. Additionally, many low surface energy materials are largely insoluble in water, and must be formulated into emulsions or suspensions (an inherent disadvantage of aqueous systems). Moreover, water of suitable quality for use in coating and impregnation is becoming less available and more expensive.
CO.sub.2 -based dry cleaning systems that contain surfactant molecules (particularly molecules having a CO.sub.2 -philic group are described in, for example, U.S. Pat. Nos. 5,683,473; 5,676,705; and 5,683,977, all to Jureller. The purpose of the surfactant molecule proposed in the Jureller patents is to carry away soil from the fabrics, rather than to become deposited upon, and seal soil to, the fabric. Surface treatment is, accordingly, neither suggested nor disclosed.
In view of the above, it is an object of the present invention to provide a method of treating and/or impregnating a substrate which does not require the use of organic solvents or water.
It is also an object of the present invention to provide a method of impregnating a substrate which minimizes adverse affects to the physical properties of the substrate.